GPAs. I was able to access the rankings via my on campus job. My then girlfriend (now wife) went to an inner city school where the focus was on just keeping order. She was valedictorian, but her weighted gpa was pretty average. I went to a public HS a few blocks from a university so most of the students had parents who considered academics to be of the utmost importance so it was ranked as one of the best public schools in the US. My weighted GPA was above 4.0.

I don't remember exactly how they used that information, but if your son's school is that much harder, he'll likely get credit for it in the admissions process.